The preparation of pure carbonyl iron powder (CIP) by decomposition of pure iron pentacarbonyl (IPC) is known, for example, from Ullmann's Encyclopedia of Industrial Chemistry, Iron Compounds, E. Wildermuth, H. Stark et al., published online: 15 Jun. 2000, (Wiley-VCH-Verlag).
For this purpose, iron particles are reacted under high pressure and at high temperatures to form iron pentacarbonyl (IPC, Fe(CO)5). The impurities present in the iron are preferably partly removed by distillation at the carbonyl stage and highly pure IPC is obtained. This compound is the precursor for the decomposition of the IPC into CIP in the subsequent step. In this step, the IPC is decomposed to CIP at high temperatures, e.g. in a downflow decomposer.
In downstream process steps, this primary CIP can be processed to produce a catalyst for the Fischer-Tropsch synthesis. The further processing and the suitability of the catalyst for the preparation of hydrocarbons, in particular lower olefins, from synthesis gas (Fischer-Tropsch synthesis) is described in the patent applications EP 07112853.2 of Jul. 20, 2007 and EP 08156965.9 of May 27, 2008 (both BASF AG or SE).
It is known that hydrocarbons can be prepared from carbon monoxide (CO) and hydrogen (H2) over metal catalysts, e.g. iron or cobalt catalysts.
Further iron catalysts for the Fischer-Tropsch synthesis are described in WO 2006/127261 A1, page 2, section [005] (precipitated catalysts) and loc. cit. section [006] (fused catalysts).
The main disadvantages in the preparation of iron Fischer-Tropsch catalysts or of precipitated catalysts in general are the energy—and labor—intensive preparation and the waste materials obtained, which usually have to be classified as environmentally harmful materials.